Has anybody ever encountered the following error message and knows what KindleGen complains about?

Code:

Error(core):E1003: Unknown error in class String.

It was displayed when I compiled a dictionary for the first time with KindleGen.
(It previously compiled without any error messages with Mobipocket Creator.)

The weird thing is that KindleGen usually stops the compilation process after displaying an error message, but it actually produced a working .mobi file after displaying the following message at the end:

I have not seen that error but it would seem to be referencing a bad character (illegal character) in one of your class statements. Look for class= in the source and inspect. It might be that that class is being ignored.